Thermoplastic molded parts, molded foils or molded skins for the interior cladding of motor vehicles are well known and are, for example, used for the interior cladding in vehicles, that is, as covering of dashboards or of door inserts or of sun visors, et cetera. Molded parts of this type are usually comprised of a multilayer plastic foil with foam on its underside which has on its upper side a three-dimensionally structured, embossed surface, namely, a so-called pattern or texture effect in a very wide variety of shapes and embodiments.
The molded parts or molded foils are comprised of a relatively hard high-density upper layer, namely the outer layer or decorative layer, which has the embossed or impressed surface, and of a low-density foam layer as lower layer applied by lamination/adhesion to the underside giving the covering an attractive feel, that is, an attractively “soft” touch characteristic. The hard upper layer here is also known as “compact foil”.
Both the upper layer and the lower layer of the molded parts/molded foils can be comprised of a plurality of layers of different or differently formulated materials, for example, of plastics, such as PVC (polyvinyl chloride), PP (polypropylene), TPO (polyolefin), et cetera or of a combination of these or similar materials.
The prior art discloses various methods for the production of molded skins of this type, for example, roll processes for the production of “continuous” foils or also processes for the production of individual molded foils falling off the tool.
In the following, rolling methods are discussed wherein a surface structure is imparted to a thermoplastic foil via an embossing process, for example, with the aid of an embossing roller.
Besides deep-drawing, several other forming methods are known for the subsequent application of such a molded part or such a molded foil to a dashboard support or to a prefabricated support part produced, for example, from fiber-reinforced cardboard, for a side-door insert. These other forming processes can be pressure processes wherein the foil is pressed against molds or against the supports mentioned and obtains the shape of the component.
United States published patent application 2005/0173047 discloses a decorative foil for, for example, dashboards, which is configured as a multilayer molded body having a plurality of lower layers and an upper layer. The upper layer comprises at least partially cross-linked polymeric materials, for example those based on polyolefins and has a foamed lower layer with specific gel content and predetermined density. The decorative foil is treated with electron beams to impart the stability of texture required during the execution of a subsequent deep-draw process. These electron beams further crosslink the foil or the molded body, thus giving it the stability needed.
This type of foil or molded body is therefore composed, as described above, of a composite of a plurality of layers whereby a relatively high consumption of materials is pregiven. Another factor with molded bodies of this type, in which the upper foil has been relatively highly crosslinked, and the foamed lower foil is also configured to be quite stable, is that they cannot be used with the airbag-trigger devices present in current mass-produced vehicles unless the foil, which, of course, covers the entire dashboard for example and therefore also the trigger mechanism/the airbag, is weakened along a seam for tearing. This weakening takes place, for example, by treatment with a laser beam, in which a laser beam burns or cuts a portion of the thickness of the foil. A disadvantage here is that in the case of certain plastics the weakness produced by the laser beam in the reverse side of the material can also become visible during the course of time on the external side, because of relaxation of the material. Since there is a marked trend toward quality improvement in the automobile interior sector, the acceptability of irregularities of this type is constantly decreasing.
German patent publication 196 53 608 B4 discloses a plastic foil which has a pleasant textile feel and which is suitable for items of apparel or household products composed of plastic. The surface of the plastic foil has a fine-cell foam structure which, if appropriate, can have been applied in the form of a foam foil on one or two sides of a support foil or support structure. The foamed layer or foamed foil here is produced from various raw materials or mixtures of raw materials while adding various foaming agents and supplementary agents. However, it is difficult here to achieve any further working of the surface involving a decorative effect or an embossment without, in turn, destroying the perceived “pleasant textile” touch, and this type of foil is therefore not very suitable for, for example, the covering of dashboards.